Since Branemark adopted titanium alloy as oral implant in sixties of the 20th century, titanium alloy has ended history as a material solely for aerospace application, and gained wide development and application in the field of biomedical material. Presently, Ti-6Al-4V alloy, also called TC4 titanium alloy, is the most widely used material in orthopedics. It is widely used as restoration material for surgery since it has excellent corrosion resistance, very good biocompatibility, high mechanical strength, and good machinability. However, research has shown Ti-6Al-4V alloy has low plastic shear resistance and undesirable work-hardening property, which is insufficient to resist friction wearing due to mechanical property impact. What's more, the Ti02 film on surface is prone to peeling, and then can not well protect the subsurface layer. Usually under normal condition, the titanium alloy will form a stable and continuous oxide passivation film on surface which possesses good corrosion resistance. But due to the complexity of human body environment and erosion of external force and body fluid, the surface passivation film could be peeled and dissolved. Therefore some substances will be released into the tissue in use. Moreover, the titanium alloy has a large friction coefficient, which leads to poor wearing resistance. Therefore large amount of Ti, Al and V black debris will be generated due to wearing of the implant, and those debris can cause sterile loosening and lead to the failure of the joint replacement.
In order to improve the performance of the medical titanium alloy, various surface treatment methods were used to modify titanium alloy surface to make it more suitable for medical application. The surface modification of the titanium alloy not only keeps characteristics of the titanium alloy as a basal body material, but also dramatically improves overall performance of the titanium alloy; thus becoming hot spot in the research of medical titanium alloy. As the development of ion implantation, plasma spraying, chemical plating, ion plating, Physical vapor deposition (PVD), Chemical vapor deposition (CVD), microarc oxidation, and laser fusion coating techniques, TiN, TiC, diamond-like-carbon (DLC), and TiO2 ceramic coat with good resistance to wearing and corrosion can be formed on the titanium alloy surface to improve bio surface wearing resistance and corrosion resistance; hydroxylapatize (HA) or bioactive glass (BG) bioactive coat also can be formed on surface of titanium alloy to prevent V and Al ions contained in the titanium alloy from releasing into physiological environment, so as to improve biocompatibility of the material. Thus it is important to research surface modification technique of titanium alloy, prepare cermet with resistances to wearing and corrosion, and study the properties of biofriction in physiological environment for developing high performance artificial joint, prolonging service life of titanium alloy artificial joint, disclosing its lubrication mechanism, and further improving stability and reliability of the artificial joint replacement.